Sharpening in Photoshop -- Part V

Article and Photography by Ron Bigelow

www.ronbigelow.com

Photoshop CS or Photoshop CS2 Used in this Tutorial

Let's start off with a warning. This article is where the fine art photographers begin to break ranks with the snapshot photographers. Up until now, the techniques have been fairly quick and easy to use (once you have built up some experience). One could, for instance, quickly create a sharpening layer, attach a mask, and apply Smart Sharpen. The time and effort involved would be reasonably small and justifiable for even a 4x6 print or a shot destined for the web. On the other hand, the sharpening methods in this and the following articles are far more sophisticated and produce far better results than what has been presented earlier in the series. Not surprisingly, these results come at a price. That price is the time investment that it takes to carry out these sharpening methods and to fine tune them. Additionally, the learning curve is longer. It doesn't take too much time to learn to get acceptable results with a one pass USM approach; it will take longer to become proficient with the following sharpening methodologies.

Conversely, as far as I am concerned, this is where it gets fun. While it is true that there has been a lot of sharpening information presented in the first four articles (perhaps far more information than many thought they even needed to know). In my mind, this previous information was all preliminary. It serves as the foundation: the science part of sharpening. Yet, as photographers, we are rarely satisfied with the science alone. It is in this article that we begin to combine that science with the art of sharpening.

This article is all about selective sharpening -- giving each part of the image exactly the type and amount of sharpening that it needs. To this end, two sharpening techniques will be introduced: sharpening masks and edge masks.

Selective Sharpening and Analysis

Producing a top quality print is a lot like creating a great meal. You wouldn't expect a gourmet chef to have only one recipe and to always prepare the exact same meal in the exact same way. Instead, we would expect a world renowned chef to have many recipes. Furthermore, we would expect that the chef would not just blindly follow the recipes. We would expect that the chef would sample his food as he prepared it and make decisions about the preparation based on his sampling: add a bit more oregano or bake a little longer.

The same follows for anyone wanting to produce a great image. Great images are not produced by following cookie cutter recipes. Rather, the photographer that wants an image to stand out from the crowd must know many sharpening recipes (like those covered in this series). Furthermore, she must analyze each image to determine its sharpening needs and develop a recipe for the image that best addresses the image's requirements. Just like the chef, she must sample her sharpening, with test prints, and make adjustments based on the sampling.

The techniques in this article are the beginning to becoming a gourmet photographer.

Sharpening Masks

Figure 1: One Pass Sharpening Problems

Up until now, we have basically prepared some type of sharpening and applied it to the entire image. This can cause problems. Revisiting an image from Part II of this series (see Figure 1) demonstrates the types of problems that can occur. As stated in Part II:

"Arrow 1 shows a window pane that has been sharpened just about the right amount. The weathered wood grain clearly shows without any oversharpening. However, arrow 2 shows another section of the window that appears less weathered. This wood did not respond as much to the sharpening; it is somewhat undersharpened. Arrow 3 shows a section of the cement like material that was used to hold the bottles in place. This part of the wall is beginning to show signs of oversharpening. So, this image is properly sharpened, undersharpened, and over sharpened -- all at the same time."

While such sharpening might be perfectly fine for everyday shots (e.g., the kids at Grandma's house, Fido the dog catching a Frisbee, and a snapshot of Mount Imaonvacation), there are times when the discerning photographer wants a more refined sharpening for her images. Sharpening masks are the first step in the direction of refinement -- and it is a large first step. The use of sharpening masks, with layers, provides a tremendous amount of flexibility in sharpening. Sharpening masks allow us to create specific sharpening for specific parts of an image.

With sharpening masks, a layer is created, as covered in Part IV of this series, and a mask is added to that layer. The sharpening is then applied to the layer. The mask allows the photographer to modify the sharpening of the layer and to restrict it to specific areas of the image. For more elaborate sharpening jobs, multiple layers can be created for the same image, each layer with its own mask. This allows different sharpenings to be created and applied to different areas of the same image.

Masks are created by using the various selection tools available in most image editing programs. The process of producing selections is far too vast to cover in this article. Thus, for the purposes of this article, it is assumed that the reader knows how to make selections.

Sharpening masks are generally used for three purposes:

  1. Masking out sharpening.
  2. Masking in sharpening.
  3. Modifying the sharpening of a layer by painting on the mask.

The following three examples will illustrate how sharpening masks can be used for these purposes.

Sharpening Masks: Masking Out

Figure 2: Masking out Sharpening Required.

Figure 2 shows an unsharpened image of a waterfall that is in prime need for masking out of sharpening during the sharpening procedure. A long exposure was taken to blur the running water and give it that traditional, smooth waterfall look. The last thing that a photographer would want to do with this image is to sharpen that nice smooth water. Doing so would give the image a rather unnatural look and would ruin the feel of the image. On the other hand, the photographer does need to sharpen the rest of the image. The solution is a sharpening mask.

Figure 3: Layer Palette

It should be realized that, in the case of this image, the image is unsharpened and the mask is being used to prevent a particular part of the image (i.e., the waterfall) from receiving any sharpening at all.

The first step was to copy the background layer as covered in the section on Layer Based Sharpening/Luminosity Mode. The Background copy layer was renamed the Sharpening Layer (see Figure 3).

Figure 4: Edit in Quick Mask Mode on the Tools palette

For this waterfall image, a selection of the water was made using the Color Range tool. Some minor editing was done to fine tune the mask. Clicking on the Edit in Quick Mask Mode on the Tools palette (see Figure 4) allowed the mask to be easily seen. Figure 5 shows the mask in the Quick Mask Mode. The areas in red have not been selected. The areas without red have been selected. It can clearly be seen that the waterfall has been selected.

Figure 5: Waterfall Mask before Blurring

 

Figure 6: Gaussian Blur tool
In order to prevent an abrupt transition between the sharpened and unsharpened areas. The mask was blurred in the Quick Mask Mode by using the Gaussian Blur tool (see Figure 6). This tool was launched by selecting Filter/Blur/Gaussian Blur. Once in the Gaussian Blur tool, the image was blurred with a three pixel radius (the radius can be adjusted to fit the needs of the image). Figure 7 shows the mask once the blurring step has been completed.
Figure 7: Waterfall Mask after Blurring
Figure 8: Edit in Standard Mode on the Tools palette

The mask was now completed and ready to be applied to the Sharpening layer. Clicking on the Edit in Standard Mode on the Tools palette (see Figure 8) moved the image out of Quick Mask mode. Figure 9 shows the image at this point in the process. The selection can be identified by the "marching ants" outline. The Sharpening Layer on the Layer Palette was then selected (look back at Figure 3). The blend mode for the layer was set to Luminosity and the opacity was set to 50%.

Figure 9: Waterfall with Selection Outlined

 

Figure 10: Layer Palette with Mask on Sharpening Layer

Applying the mask to the Sharpening Layer was an easy process by selecting Layer/Layer Mask/Hide Selection. The Sharpening Mask now had a mask as seen in Figure 10. The white areas on the mask allow the sharpening to be applied. The black areas are masked out. No sharpening will be applied in the black areas.

Figure 11: Sharpened Image

The Sharpening Layer was then sharpened with USM as described in the Unsharp Mask section. The Opacity and Blend-if controls were adjusted as described in the Layer Based Sharpening/Luminosity Mode section. The mask applied the sharpening to the rock, but the water was protected from the sharpening by the mask. The final result can be seen in Figure 11.

Sharpening Masks: Masking In

Figure 12: Sharpened Image that Requires Additional Sharpening for the Moon

In the prior example, it was desired to protect part of an image from sharpening. In this example, the exact opposite is desired. Figure 12 shows an image that has already received some sharpening (via a plug in that will be covered in a later part of this series). Figure 13 shows the Layers Palette. The layers from the prior sharpening steps can be seen on the palette (notice that this layer already has a sharpening mask on it to protect the sky from being sharpening).

However, while most of the image has been adequately sharpened, for this stage of the workflow at least, the moon could use a small amount of additional sharpening. On the other hand, it is necessary to provide the supplementary sharpening without increasing the sharpening of the rest of the image. Again, the solution is a sharpening mask.

Figure 13: Layers Palette Showing Prior Sharpening Layer
Since the procedure of creating and applying the mask is similar to the prior example, we will not go through the step-by-step procedure. However, Figure 14 shows how the selection appears. Figure 15 shows the Layers palette after the mask has been added to the layer. The one difference with this image, as compared to the prior one, is that the mask was applied to the layer by selecting Layer/Layer Mask/Reveal Selection (the prior image used Layer/Layer Mask/Hide Selection).
Figure 14: Moon Mask
Figure 15: Layers Palette with Additional Layer for Sharpening the Moon
For the final steps, the Sharpen Moon layer was sharpened with appropriate sharpening tools and techniques, and the sharpening controls were adjusted to deliver the desired sharpening.

Layer Painting

Figure 16: Major Sharpening Problem with halos

Sometimes, it is best to simply paint sharpening in or out. Sharpening layers work great for that purpose too. Figure 16 shows a section of an image that has a major problem. The sharpening that was appropriate for most of the image produced pronounced halos along the areas where the old building was backlit by the sky.

Figure 17: Layers Palette Showing Sharpening Layer

Figure 17 shows the Layers palette. The Sharpen layer can be seen with a white mask already applied. Since any white area on a mask allows the sharpening to be applied, this mask allows the sharpening to be applied everywhere in the image (in other words, the mask does absolutely nothing at this point). If the mask was missing, a white mask could be applied by picking the Sharpen layer and selecting Layers/Layer Mask/Reveal All.

To eliminate the halo problem, the Brush tool was selected from the Tools palette (see Figure 18). The Tool Preset menu allowed the brush to be configured for the task at hand (see Figure 19).

 

Figure 18: Brush Tool on Tools Palette
Figure 19: Tool Preset Menu

Since the halos were very narrow, the Master Diameter was set very small. The hardness was set to 100% so that drawing could be done very precisely without a reduction in sharpening due to the mask bleeding over into the wood (a low hardness setting would have blurred the lines drawn on the mask; this blurring of the lines would have caused the edges of the mask to bleed over into the wood). The Mode was set to normal. The Opacity was set to 100% so that the mask would completely block out the sharpening in the masked areas. The foreground color was set to pure black on the Tools Palette (see Figure 18).

Double clicking on the mask of the Sharpen layer while holding down the Alt key moved the brush into the mask editing mode. Painting with the brush on the image actually painted on the mask. Since the brush was set to black, the process painted black on the mask. The brush was used to merely paint over the halos. As a result, the halos just disappeared.

Moving the image to the Edit in Quick Mask Mode on the Tools palette (as covered in the first example), revealed the mask (see Figure 20). The final image, without the sharpening halos, is shown in Figure 21.

Figure 20: Mask to Remove Sharpening Halos
Figure 21: Image after Masking Out Halos

The Power of Layers with Sharpening Masks

It is important to understand the amount of flexibility, and therefore the power, that the use of sharpening masks along with layers provides. With this approach, the photographer can adjust the sharpening by:

  1. Which sharpening tool is utilized (e.g., USM or Smart Sharpen).
  2. The controls on the sharpening tools.
  3. Adjusting the Opacity control.
  4. Adjusting the Blend-If control.
  5. Changing the shape of the mask.
  6. Changing the density of the mask by painting on the mask.

Multiple Sharpening Layers

The examples shown in this article each worked on one layer. This was done to illustrate the principle without making it overly complicated. However, in working with complex images, there can be several sharpening layers, each with its own mask, with each mask aimed at solving a particular sharpening issue. The only drawback is that each additional layer will create a larger file and slow down the computer (Hey, Honey, Ron said that I need a new computer).

Edge Masks

We have come a long way from the one pass USM on the background layer approach with which we started. We have come to the point where we have different tools, each with its own adjustments, and the ability to create layer based sharpening with masks and Blend If controls. What could be the next step in our development of sharpening refinement? What would give us even more control? Well, wouldn't it be great if we could adjust the sharpening according to the detail of the image -- major detail could get large amounts of sharpening to make it really stand out, lesser detail would get more moderate amounts of sharpening, and smooth areas would get no sharpening. This is exactly what edge masks do!

Edge masks are masks that are based on the detail of the image. Basically, the edge mask approach singles out the edges and creates a mask that identifies the edges. The more significant the edge, the more it stands out in the edge mask. The sharpening is then performed on a sharpening layer to which the edge mask has been applied. The edge mask allows the sharpening to be applied to the major edges at full strength, minor edges at a reduced strength, and smooth areas at little or no strength.

There are many ways to produce edge masks, but they are not all equal. We will look at two ways: the easy way and the right way. Okay, so that was a bit cynical. Let's call them the easy edge mask approach and the detailed edge mask approach.

Edge Masks: Getting Started

Figure 22 shows an old ore processing plant hidden in the California mountains, which was photographed in the very soft, warm, late afternoon sun. This image is prime for the use of edge masks. A crop of the image is shown in Figure 23. It can be seen that the old boards of the plant hold a tremendous amount of detail mixed in with some smooth areas. Traditional sharpening would sharpen the smoother areas along with highly textured areas. The use of edge masks will allow the textured areas to receive more sharpening than the smoother areas.

Figure 22: Mining Ruins

 

Figure 23: Crop of Mining Ruins

Edge Masks: Easy

Figure 24: Channels Palette

The easy edge mask approach takes a bit less effort than the detailed approach, but as will be seen later, it comes at price. The process starts with the Channels palette as shown in Figure 24. Clicking the Create a New Channel icon at the bottom of the palette will create a new channel. This channel should be renamed the Sharpen Selection channel (see Figure 25).

Figure 25: Channels Palette with a New Channel

 

Figure 26: Channels Palette with the Image Pasted into the Sharpen Selection Channel

The RGB channel is now selected and the entire image is selected by selecting Select/All. The image is copied by selecting Edit/Copy Merged. The Sharpen Selection channel is selected and the image detail is pasted into the channel by selecting Edit/Paste (see Figure 26). The image at this point is shown in Figure 27. As can be seen, the image is a black and white copy of the original color image.

 

Figure 27: Image Pasted into the Sharpen Selection Channel
Figure 28: Image after the Find Edges Tool

In the next step, the edges are isolated by using the Find Edges filter, which is run by selecting Filter/Stylize/Find Edges. Figure 28 shows the image after the Find Edges Filter has been run. At this time, the edges are shown in black.

It is now necessary to increase the contrast of the image to make the edges stand out even more. This is done by using the Levels tool. The Levels tool is launched by selecting Image/Adjustments/Levels. The Shadow slider is moved to the right, and the Highlight slider is moved to the left (see Figure 29).

 

Figure 29: Levels Tool
Figure 30: Image after the Levels Adjustment

The image after the Levels adjustment can be seen in Figure 30.

The next step requires that the image be blurred to soften the mask so that the dark to light transitions are not so abrupt. This is done by using the Gaussian Blur tool. To run this tool, select Filter/Blur/Gaussian Blur. Figure 31 shows the Gaussian Blur tool. The radius setting is determined by the detail of the image. Usually, I find a setting of 3 or a bit larger to work well. In this image, the fine detail required a very small radius of about 0.8.

Figure 31: Gaussian Blur Tool

 

Figure 32: Image after the Gaussian Blur

The blurred image is shown in Figure 32. We want to use this image to create a mask. However, the edges are defined in black. A resulting mask would block out the edges -- the exact opposite of what we want. So, the image needs to be inverted by selecting Image/Adjustments/Invert. The inverted image is shown in Figure 33.

Figure 33: Image after Inverting

The image will automatically be stored as a selection.

Figure 34: Layers Palette after the New Layer was added

The next steps are performed on the Layers palette. A new layer is created and the other layers effects are merged into the new layer (as covered in the all-layer sharpening portion of the Layer Based Sharpening/Luminosity Mode section). The new layer is renamed the Sharpening layer. The Layers palette at this stage of the process is shown in Figure 34.

Next, the Sharpening layer is selected and the mask that was just created is loaded by selecting Selection/Load Selection. In the Load Selection menu, the Channel should be set to Sharpen Selection and the Invert option should be unchecked (see Figure 35). Clicking OK loads the selection. The image with the selection is shown in Figure 36.

Figure 35: Load Selection Menu
Figure 36: Image with Selection

The selection is used to add a mask to the Sharpening layer by selecting Layer/Layer Mask/Reveal Selection. The Sharpening layer Opacity is set to 50% (so that adjustments to the sharpening can be made later) and the Blend mode is set to Luminosity (so that the sharpening will only affect the tonality to avoid color fringing). The Layers palette now has the Sharpening layer with a new edge mask as shown in Figure 37.

The final step is to apply the sharpening via the preferred sharpening tool and to fine tune the sharpening as covered in the Layer Based Sharpening/Luminosity Mode section. For this image, the Smart Sharpen tool was used. The final result is shown in Figure 38.

Figure 37: Layers Palette with Sharpen Layer and Edge Mask

 

Figure 38: Sharpened Image
This image is destined for inkjet printing, so the image should look somewhat oversharpened at 100% view, as is the case in Figure 38.

Edge Masks: Detailed

The easy edge mask approach allowed for the sharpening to be adjusted for the detail of the image. This accentuated the detail when the sharpening was applied. However, the detailed edge mask approach can extract even more detail and create yet a better mask -- resulting in an even more refined detail sharpening.

The detailed edge mask approach also starts off with the channels palette. However, with this approach, each of the three channels must be examined to determine which contain the most detail. Figures 39 to 41 show the three channels for the current image. It can be seen that the Red channel has little detail. The Green channel has much better detail. The Blue channel has very contrasty detail.

Figure 39: Red Channel
Figure 40: Green Channel
Figure 41: Blue Channel
Figure 42: Layers Palette

What is desired is to create a black and white image, from the original image, that contains as much detail as possible. For the next steps, we move back to the Layers palette (see Figure 42).

Figure 43: Layers Palette with Two New Layers Added

Before proceeding any further, a new layer is created and the other layers effects are merged into the new layer (as covered in the all-layer sharpening portion of the Layer Based Sharpening/Luminosity Mode section). This layer is renamed the Mono layer (short for monochromatic). This layer is immediately duplicated. The duplicated layer is renamed the Sharpen layer. Lastly, the Sharpening layer is hidden by clicking the eye icon (you can still see the layer, but the layer will not affect the image until it is unhidden). The Mono layer is then reselected. The current state of the Layers palette is shown in Figure 43.

The tool of choice to turn the Mono layer into a black and white layer with the most detail possible is the Channel Mixer. The advantage of using the Channel Mixer over the method used in the easy edge mask approach is that the Channel Mixer allows the photographer to choose how much detail she pulls out of each channel. This allows the photographer to fine tune the Mono layer to contain the maximum amount of detail. With the Mono layer selected, the Channel Mixer is launched by selecting Image/Adjustments/Channel Mixer. The Channel Mixer is shown in Figure 44.

Figure 44: Channel Mixer
The monochrome option is checked. The Red, Green, and Blue sliders are adjusted to maximize the amount of detail. Moving a slider to the right increases the amount of detail taken from that channel. Conversely, moving the slider to the left decreases the amount of detail taken from that channel. The Constant slider is used to adjust the overall brightness of the image. For this image, the green and blue sliders were moved to the far right to get the maximum amount of detail out of the Green and Blue channels (which held most of the image detail). The Red slider was moved to the left since that channel had relatively little detail. Clicking OK converts the Mono layer to black and white. Figure 45 shows the Mono layer after the Channel Mixer was used.
Figure 45: Mono Layer after Channel Mixer was Used

The Find Edges filter is again used to isolate the edges (select Filter/Stylize/Find Edges). Figure 46 shows the Mono layer after the Find Edges Filter has been run. At this time, the edges are shown in black.

Figure 46: Mono Layer after the Find Edges Tool

 

Figure 47: Levels Tool

As before, the Levels tool is used to increase the contrast of the image (select Image/Adjustments/Levels). Figure 47 shows the Levels tool. Figure 48 shows the Mono layer after the Levels Tool adjustment.

Figure 48: Mono Layer after Levels Tool

 

Figure 49: Gaussian Blur tool

Again, as before, the Gaussian blur tool is used to soften the mask so that the dark to light transitions are not so abrupt (select Filter/Blur/Gaussian Blur). Figure 49 shows the Gaussian Blur tool. An incredibly small blur radius of 0.2 was used for this image (normally a larger radius of 3 to 5 would be used, but this detail is very fine). Figure 50 shows the Mono layer after the Gaussian Blur adjustment.

Figure 50: Mono Layer after Gaussian Blur tool

 

Figure 51: Mono Layer after Inverting

The edges of the Mono layer are still defined in black. So, the image needs to be inverted by selecting Image/Adjustments/Invert. The inverted image is shown in Figure 51.

It is now time to turn all that hard work into a selection and then an edge mask. We go back to the Channels palette and select the RGB channel. The Load Channel as Selection icon at the bottom of the palette is clicked (see Figure 52). The Mono Layer is turned into a selection.

Figure 52: Channels Palette

 

Figure 53: Layers Palette

Returning to the Layers palette (see Figure 53), the Sharpen layer is selected and the eye icon is clicked to unhide the layer. The selection has been applied to the layer as seen in Figure 54.

Figure 54: Sharpen Layer with Selection

 

Figure 55: Sharpen Layer with Mask

The selection is used to add a mask to the Sharpen layer by selecting Layer/Layer Mask/Reveal Selection. The Sharpen layer Opacity is set to 50% (so that adjustments to the sharpening can be made later) and the Blend mode is set to Luminosity (so that the sharpening will only affect the tonality to avoid color fringing). The Layers palette now has the Sharpen layer with a new edge mask. At this point, the Mono layer no longer has any value, so it is deleted. The Layers palette is shown in Figure 55.

The final step is to apply sharpening via the preferred sharpening tool to the Sharpen layer and to fine tune the sharpening as covered in the Layer Based Sharpening/Luminosity Mode section. For this image, the Smart Sharpen tool was used. The final result is shown in Figure 56.

Figure 56: Sharpened Image

 

Why Bother with the Detailed Approach

Not surprisingly, the detailed edge mask approach requires more work than the easy approach. Why bother with the extra effort? The answer resides in comparing images from the two approaches. Figure 57 and 58 show the final, sharpened images from the two masking approaches. Figure 58 shows that the detailed approach resulted in better detail sharpening in the boards in the lower right of the image. This is because the Channel Mixer allowed for fine tuning of the detail when creating the mask.

Figure 57: Easy Edge Mask
Figure 58: Detailed Edge Mask
So, why did I even bother introducing the easy masking approach? Because, there are many techniques out there to create edge masks, but they are not all equal as far as their ability to resolve fine edge detail. Someday, someone is likely to inform you that they have a much easier method of creating edge masks than this detailed approach. They may be right; their approach may be easier. However, it may also result in an inferior mask - thus, inferior sharpening results.

Edge Masks: Even More Power

Edge masks provide the ability to adjust the sharpening to the detail of the image. This is a huge advantage over the other sharpening approaches. To further increase the power of edge masks, they can be combined with sharpening masks (of course you will need to understand how to combine masks, which is beyond the scope of this article). Since edge masks can be combined with sharpening masks and are layer based, they have all of the adjustability of sharpening masks where the sharpening can be adjusted by:

  1. Which sharpening tool is utilized (e.g., USM or Smart Sharpen).
  2. The controls on the sharpening tools.
  3. Adjusting the Opacity control.
  4. Adjusting the Blend-If control.
  5. Changing the shape of the mask.
  6. Changing the density of the mask by painting on the mask.

In addition, edge masks provide for the following new adjustability:

  1. Adjusting the Channel Mixer.
  2. Adjusting the contrast with the Levels tool.
  3. Adjusting the blur with the Gaussian Blur tool.

Higher Levels of Sharpening

Since edge masks sharpen only the edges, higher amounts of sharpening can be used without degrading other areas of the image. This is a particular advantage when producing larger prints. Larger prints require larger amounts of sharpening, but the higher sharpening amounts tend to degrade the finer detail in the image. The use of edge masks allows the photographer to get around this problem. Thus, edge masks are one key to producing high quality, large prints.

Two Pass Sharpening

Edge masks also open up the opportunity to utilize a two pass sharpening approach. In the first pass, edge masks are used to sharpen the more significant edges in the image. Since only the edges are being sharpened, larger sharpening amounts can be used. This will make the major detail really come to life. A second sharpening can then be carried out on a separate layer. This sharpening does not use an edge mask. Rather it is aimed at sharpening the fine detail in the image. For this purpose, a fairly low level of sharpening is applied.

Articles

Sharpening -- Part IV     Sharpening -- Part VI